boards/remote-revb: Update broken link in readme

make: fix info-objsize column name position

pkg: add libb2 (BLAKE2)

nanocoap: add server-side block2 support

tools/pr_check: adapt for label categorization

Doc: initial RIOT developer memo + directory structure

net: add full CoRE Resource Directory endpoint implementation

sys/arduino: add docs for analog map (strictly needed to build)

sys/arduino: add possibility to customize Arduino serial port at compile time

drivers/hd44780: fix compilation errors

boards/nrf52xxxdk: make reset pin work

boards: always include cpu features

The file always exist so no need to do '-include'.

Replaced using:

    sed -i 's|-\(include $(RIOTCPU)/.*/Makefile.features\)|\1|' \
        $(git grep -l  '$(RIOTCPU)/.*/Makefile.features' boards)

This prepares for being able to always include Makefile.features
globally. It prevents new board for missing this until it is done.

cpu/stm32_common: fix source selection declared as module dependencies (broken)

doccheck: exclude dist/tools directory from group check

The `periph_flash_common` feature was only defined here to trigger
inclusion of a source file with common functions.
It even only defines private symbols `_lock` and `_unlock` so no reason
to expose it to the build system.
And in practice, all stm cpus providing `periph_flashpage` or
`periph_eeprom` were required to provide `periph_flash_common` to allow
including it.

The previous implementation was only parsing in the modules were in
`FEATURES_REQUIRED` wich did not take cases of `FEATURES_OPTIONAL` into
account.
And also, in the same time, as the dependencies was declared in
`Makefile.include` it was processed before `Makefile.dep` so never handled
cases where a module could depend on `periph_flashpage` or
`periph_eeprom` feature.

It is replaced by selecting the common source file when module using it
are included.

The now useless feature `periph_flash_common` is removed from
`FEATURES_PROVIDED`.

`cpu/stm32_common/Makefile.dep` was never included by the global
`Makefile.dep`, so declaring this `USEMODULE +=` here was never shown to
the build system and never exported as `MODULE_PERIPH_I2C_X` variables.

In fact, `USEMODULE` was only used to trigger the `periph.mk`/`SUBMODULES`
mechanism to add matching source files names to `SRC` and so select
the implementation for each CPU type.

It is replaced by just explicitly selecting the right source file.

misc: use correct hauke.petersen@fu email address

net/rdcli_simple: do not send CF opt in POST msg

dist/tests/if_lib: Update to riot_pal